1 files changed, 53 insertions, 0 deletions
diff --git a/apps/web/src/lib/timeline/zoom-utils.ts b/apps/web/src/lib/timeline/zoom-utils.ts
new file mode 100644
index 00000000..49f7fcb6
--- /dev/null
+++ b/apps/web/src/lib/timeline/zoom-utils.ts
@@ -0,0 +1,53 @@
+import { TIMELINE_CONSTANTS } from "@/constants/timeline-constants";
+
+const PADDING_MAX_RATIO = 0.75;
+const PADDING_MIN_RATIO = 0.15;
+const PADDING_MIN_AT_ZOOM_PERCENT = 0.2;
+
+export function getTimelineZoomMin({
+	duration,
+	containerWidth,
+}: {
+	duration: number;
+	containerWidth: number | null | undefined;
+}): number {
+	const safeDuration = Math.max(duration, 1);
+	const safeContainerWidth = containerWidth ?? 1000;
+	const contentRatioAtMinZoom = 1 - PADDING_MAX_RATIO;
+	const availableWidth = safeContainerWidth * contentRatioAtMinZoom;
+	const zoomToFit =
+		availableWidth / (safeDuration * TIMELINE_CONSTANTS.PIXELS_PER_SECOND);
+
+	return Math.min(TIMELINE_CONSTANTS.ZOOM_MAX, zoomToFit);
+}
+
+export function getTimelinePaddingPx({
+	containerWidth,
+	zoomLevel,
+	minZoom,
+}: {
+	containerWidth: number;
+	zoomLevel: number;
+	minZoom: number;
+}): number {
+	const zoomPercent = getZoomPercent({ zoomLevel, minZoom });
+	const paddingTransitionPercent = Math.min(
+		zoomPercent / PADDING_MIN_AT_ZOOM_PERCENT,
+		1,
+	);
+	const paddingRatio =
+		PADDING_MAX_RATIO -
+		(PADDING_MAX_RATIO - PADDING_MIN_RATIO) * paddingTransitionPercent;
+
+	return containerWidth * paddingRatio;
+}
+
+export function getZoomPercent({
+	zoomLevel,
+	minZoom,
+}: {
+	zoomLevel: number;
+	minZoom: number;
+}): number {
+	return (zoomLevel - minZoom) / (TIMELINE_CONSTANTS.ZOOM_MAX - minZoom);
+}